Production of eight 150MHz digital frequency meter, 150MHz Digital Frequency Meter
Keywords: digital frequency gauge, 150M frequency meter circuit
When making a high-frequency circuit, the problem of frequency measurement is often hitting, and the actual frequency counter is a relatively easy homemade electronic device. The frequency meter to be made is not inferior to the products manufactured by the general manufacturer. The resulting frequency meter is as follows: (1) Displayed bits: 8-digit LED (2) frequency test range: 10Hz ~ 10MHz, use preset divider (PRESCALER) to do 1/100 division, can 150MHz (3) Benchmark Time Stability: Due to the use of TCXO units (temperature compensation type crystal oscillator circuit), temperature characteristics ± 3 ppm / -20 ~ 60 ° C aging rate ± 1 ppm / year. The above indicator parameters reach even more than the frequency meter index parameters produced by the general manufacturer.
The resulting frequency gauge diagram (main circuit is an input amplifier, PRESCALER, display. Except, Wang's control circuit, counting circuit, display circuit, etc., each already included in the frequency of the LSI.) Frequency Method for forming the frequency meter made of a frequency meter, Figure 38 is a circuit diagram thereof. Hereinafter, it will be explained for the block diagram. Preparation of frequency meter circuit schematic
▲ count (calculating) LS heavy; this production uses ICM7216B (Intersil). The interior of this IC contains 8-digit BCD counter, BCD to 7 byte decoder Segment Decoder, control circuit, etc. If you append, the peripheral broadband amplifier, the LED trick, etc. can complete the frequency gauge. ▲ The reference time signal generates the main parameter indicator of the TCXo unit, it can be seen that it has a considerable frequency stability performance. The oscillation frequency of TCXO is 12.8MHz, using IC 74HC4060 with divided by IC 74HC4060, is divided by 1/12 8, and then the reference frequency is 100 kHz supply frequency based on LSI.
Temperature compensation type crystal oscillator TCXO TCO · 703A characteristics (due to the internal temperature compensation circuit, the frequency stability is good. The oscillation frequency is 12.8MHz, and the reuse divided by IC74HC4060 is divided into 100KHz.
TCXO TCO-703A Performance Index Parameter Output Frequency 10MHz 12.8MHz or 14.5MHz Power Supply Voltage 5V ± 5% Work Power ≤5mA Output Level 1VP-P Load 20kΩ // 5PF Frequency Stability Temperature Features ± 3PPM / -20 ~ 60 ° C Power supply variation feature ± 0.3ppm / 5V ± 5% long-term feature ± 1ppm / (year) frequency adjustable range is greater than (including repair capacitor) with a series of products available 10MHz ~ 24MHz
▲ The front frequency divider circuit is 10 MHz because the frequency of the ICM 7216b is 10MHz, and the front divider can improve the frequency of application caps. The front frequency divider circuit diagram shown in Fig. 41 is a proof of 1/100.
▲ Other circuit frequency meters The output of the output or the output of the broadband amplifier is switched between the output of the wideband amplifier or the output of the 3 state buffer (3 State Buffer) as a switch as a switch, as shown in FIG. 41.
L / 100 Dividend Pretreatment circuit (the maximum input frequency of the 200,000 frequency is only 10MHz, so the preset divider is used to divide the frequency range of the test, and the frequency range of the test can be expanded.) Configure the part configuration and the printed circuit board pattern with the adjustment diagram 42. On the printed circuit board, a rectifier circuit and a regulator circuit are included. Numerical Display LEDs use eight common cathode (COMMON CATHODE) LEDs, and the size of the size can be well observed. Of course, if the LEDs that cannot be obtained, the LED specification can be obtained, and the printed circuit board is necessary to modify. Figure 43 shows the part of the front divider and a copper foil pattern of the printed circuit. After the substrate is completed, the set electrode voltage of 2SC2347 is adjusted to 2.5 V using the VR 10K of the wideband amplifier. Others don't need to be adjusted, find a beautiful shell to put the entire circuit, and the production of the entire frequency is completed.
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